JPH0352272B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording and reproducing device (hereinafter abbreviated as VTR).

As is well known, general VTRs are mainly of the two-head helical scan type, in which two video tracks mounted on a rotating cylinder alternately pass magnetic tape wound around the cylinder at an angle of about 180 degrees. Scan, record and reproduce signals. Further, signals are exchanged between the rotating video head and the recording/reproducing signal processing circuit via a rotary transformer, and there is no signal processing circuit on the rotating cylinder.

Recently, newly developed recording technology and video head tracking technology are being applied to VTRs, and while these technologies bring great advantages, they are also creating new problems. First, I will briefly discuss these.

One of these is a technology in which the audio signal is frequency multiplexed with the FM modulated signal and the video recording signal, and then recorded on the same video track by a video head.
(A well-known example is Japanese Patent Publication No. 39-9565.) This is less susceptible to mechanical wow and flutter, provides good reproduced sound with little frequency fluctuation, and provides rich reproduced sound with a wide transmission frequency band. On the other hand, there is a problem in that instantaneous noise is likely to occur due to dropout of the playback signal, and post-recording (re-recording only the audio signal while leaving the video signal unchanged) is not possible.

In addition, the magnetic tape is wound around a rotating cylinder at an angle of 200 to 220 degrees, and an overlap section is provided on the extension of the video track, which is formed when two video heads simultaneously scan the magnetic tape. There are also proposals to record the audio signal with a video head. Since this overlap portion exists discontinuously in time, the signal must be compressed once in the time axis. (As a publicly known example,
There is −2724. ) In this case, since it is recorded at a location different from the video signal, dubbing becomes possible. Of course, I thought this was only for dubbing, and
It can also coexist with FM modulation multiplex recording.

In order to improve the tracking accuracy of the video head, this is mounted on an electrostrictive element such as a bimorph plate, and a control signal is applied to the electrostrictive element during playback so that the video head accurately traces the recording track. A technology has also been developed to do so. The control signal is also obtained from a pilot signal frequency multiplexed onto the video track, but since this is already well known, the details will be omitted. (A well-known example is the Philips VTR, model V-2000.) Furthermore, there is a proposal to control the height of the video head using this electrostrictive element during recording as well. In other words, it is quite difficult to match the heights of two video heads simply by adjusting the mounting screws, and the heights of the two video heads may become incorrect due to changes over time. Therefore, an attempt is made to control the recording time so that it always matches. Specifically, only a signal of a specific frequency is recorded for the length of one to two horizontal periods of the video signal at one location on each track formed diagonally on the magnetic tape, and then When one video head is recording an adjacent track, when it comes to a position adjacent to the recorded portion of the signal, the signal circuit system of that channel is momentarily switched to playback mode, and the signal from the adjacent track is recorded. is reproduced, the circuit system is immediately switched to the recording mode, and a recording portion of the signal is also formed for one to two horizontal periods on the track being formed. (Note that the timing of recording and playback is reversed depending on how the track is formed.) By repeating this operation, electrostriction is applied so that the playback output of the signal from both video heads is equalized (or both are made zero). By applying a control voltage to the element, the heights of the two video heads can be conveniently adjusted each time recording is performed.

However, this height control during recording has two major problems. One is interference with FM modulated audio signals that are multiplexed onto video tracks.
There is no recording signal of video, audio, etc. not only in the portion where the above-mentioned signal circuit momentarily switches to the playback mode but also in the portion where the height control signal is recorded. Therefore, if this part is in the part where the video signal and the FM modulated audio signal are multiplexed and recorded, these pieces of information will repeat the instantaneous drop-out phenomenon during playback. As for the video signal, put it in a vertical blank period, etc.
Although it is possible to prevent the noise from appearing on the television screen, such a measure is not possible for audio signals, and there is a problem in that significant noise is generated in the reproduced sound.

The second problem is as follows. Although it has been described that one video head performs a playback operation momentarily during recording, it is not always possible to have the other video head perform a playback operation at the same time. That is, as mentioned above, there are currently some devices that perform overlapping recording by wrapping a magnetic tape around a rotating cylinder at an angle of 180 degrees or more. In this case, both video heads may be on the magnetic tape, and if they are reproduced at the same time, a completely meaningless drop-out period will be created in addition to the height control signal recording/reproducing section. The other video head must therefore continue recording. However, the reproduced signal is generally about 80 dB smaller than the recorded signal. If both of these exist at the same time, the reproduced signal will be seriously disturbed and will no longer be able to perform its original function. For example, if you want to achieve an isolation of 50 dB or more between two electrical systems that are located close to each other, you must give careful consideration to their placement, but in this case, even if you reach 80 dB, the reproduction signal and the Since it is only possible to make the leakage of the recording signal to the same level (actually, it is necessary to make it equal to the level), there is a problem in that it is difficult to sufficiently achieve the intended purpose.

An object of the present invention is to solve the above-mentioned problems in controlling the height of a video head during recording, eliminate interference with audio signals caused by this, and eliminate interference with height control signals during playback. The aim is to provide methods and means to make this problem free of practical problems.

That is, first, the height control signal is recorded and reproduced at a position other than the part where the video signal and the audio signal as an FM modulated wave are recorded, thereby eliminating interference with the audio signal. In addition, by incorporating at least a reproducing amplifier in the rotary cylinder to amplify the reproducing output of the video head in the recording/reproducing signal circuit, good isolation between the recording signal and the reproducing signal is achieved, and the video output during recording is improved. The idea is to make it possible to control the height of the head in accordance with the desired performance.

Next, embodiments of the present invention will be described with reference to the drawings. FIGS. 1 and 2 illustrate part of the recording pattern that remains on the magnetic tape when the present invention is implemented. 1 is magnetic tape, 2 is video signal and FM
This is a video track in which a modulated wave and an audio signal are frequency-multiplexed and recorded. 3 is hereinafter referred to as an overlapping track. This is a track that is an extension of the video track 2 and is made by winding the magnetic tape 1 around a rotating cylinder by more than 180 degrees, and records, for example, digitized audio signals. Reference numeral 4 indicates a recording portion of a signal for controlling the height of the video head during recording, and reference numeral 5 indicates a blank portion generated by momentarily reproducing this height control signal in the video head during recording.

The first problem mentioned above, that is, interference with the FM modulated audio signal by recording and reproducing the height control signal, is that the recording pattern on the magnetic tape is
This problem can be solved by doing as shown in FIGS. That is, the recorded portion 4 of the height control signal and the blank portion 5 are transferred to the overlapping track 3.
It is preferable to locate it in the middle (FIG. 1) or adjacent to the boundary between this and the video track 2 (FIG. 2). In other words, it may be located at a location other than video track 2. Of course, you can set this location as you like. Also, since the overlapping track 3 originally records a time-base compressed signal, there is no problem even if a part of it is occupied by the above 4 and 5, and by changing the compression method, It is possible to essentially avoid interference.

Next, we will discuss how to solve the second problem, which is that it is difficult to instantaneously reproduce the height control signal of the video head due to the problem of isolation from the recording signal applied to one video head. First, let's consider why isolation deteriorates.

The isolation between the two video heads in current VTRs is partly due to the circuit elements, but it is essentially due to the wires and rotary transformers that connect the video heads and the signal recording/reproducing circuit. many. That is, electromagnetic coupling between wires and magnetic coupling between both channels of a rotary transformer. However, the former problem can be improved by making the wires shorter, especially by making the wires between the video head and the regenerative amplifier as short as possible. The latter can be achieved by using a known transformer core for both channels (as a known example, a 1-inch broadcasting
(There is a rotary transformer for VTR) This can be improved from the current situation. In addition, if the problem becomes serious because the playback signal level is originally much lower than the recording signal level, as in the example above, the playback signal should be amplified until its level is approximately the same as the recording signal level, and then the rotary If you pass it through a transformer, there will be no problem at all.

Therefore, in the present invention, among the signal recording and reproducing circuits, at least a reproducing amplifier for amplifying the reproduced signal from the video head is built into the rotary cylinder. In this way, the wire between the video head and the reproducing amplifier can be made extremely short, and the weak reproduction signal is amplified by the reproducing amplifier and then applied to the rotary transformer, so the isolation problem mentioned above is eliminated, and the The height of the head can be controlled stably.

FIG. 3 is a circuit block diagram showing an embodiment of the present invention described above, in which 6 is an input terminal, 7 is a recording amplifier, 8 is a recording/reproduction changeover switch, 9 is a rotary transformer, 10 is a video head, and 11 is a magnetic 12 is a reproducing amplifier, and 13 is an output terminal.

During recording, the video head 1 is connected to input terminal 6.
Different types of signals are input depending on the position of 0 on the magnetic tape 11. That is, when the video head 10a is located at the video head height control signal recording portion 4 of the overlap track 3 shown in FIGS. When it is at a position other than that, for example, a digitized audio signal is input from the input terminal 6a. When the video track is located, a frequency multiplexed signal of a video signal and an audio signal converted into an FM modulated wave is inputted from the input terminal 6a. The relationship between the position of the video head 10b and the input signal at the input terminal 6b is also the same. The data is then applied to the video head 10 via the recording amplifier 7, switch 8, and rotary transformer 9, and recorded on the magnetic tape 11 as shown in FIGS. 1 and 2 above. On the other hand, during playback, all the switches 8 are connected in the opposite direction to that shown. The playback signal from the video head 10 is amplified by a playback amplifier 12 which is built on a rotating cylinder like the video head and connected to it via an extremely short wire, and then sent to an output terminal via a rotary transformer 9. 13.
Needless to say, the reproduced signal is then divided according to the recording on the magnetic tape of the video head 10 and sent to each signal processing circuit. Also, when the video head 10 is located in the blank area 5 in Figures 1 and 2 during the previous recording, only that channel is played back, but the flow of the playback signal at this time is the same as during playback above. be.

It will be clear that if this is done, the above-mentioned isolation problem will be eliminated.

Although the electrostrictive element on which the video head 10 is mounted is omitted in FIG. 3, the present invention is premised on the presence of this element.

Similarly, in Fig. 3, we have explained the case where only the reproduction amplifier circuit (or a part of it) is built on the rotary cylinder, but if necessary, the recording amplifier or other signal processing circuits may also be included together with it. It may be built-in, and in this case as well, the same effects as in the above embodiment can be achieved.

Furthermore, FIG. 4 shows an embodiment different from that shown in FIG.
Here, the components other than the rotary transformer 14 and the regenerative amplifier 15 at the rear stage may be the same as those shown in FIG. That is, if the recording system and the reproducing system are further separated and a four-channel rotary transformer 14 is used, only two selector switches 8 are required. Also, the regenerative amplifier 15 at the rear stage
is added if the gain of the regenerative amplifier 12 alone is insufficient to sufficiently operate the subsequent signal processing circuit. If unnecessary, it may be omitted, and the gain of the regenerative amplifier 12 may be further increased to provide this function.

As explained above, the present invention records and reproduces a signal for controlling the height of a video head mounted on an electrostrictive element during recording at a position other than the video track, and also controls the recording and reproduction signal circuit. Among these, the idea is to incorporate at least a regenerative amplifier into the rotating cylinder.

For this reason, the FM recorded on the video track
The disturbance of the height control signal to the modulated audio signal can be completely eliminated. Further, when the height control signal is instantaneously reproduced, the interference of other signals with respect to the reproduced signal can be much reduced compared to the conventional method, and there are effects such as excellent video head height control.

[Brief explanation of drawings]

1 and 2 are recording pattern diagrams on a magnetic tape when the present invention is implemented, FIG. 3 is a circuit block diagram showing an embodiment of the present invention, and FIG. 4 is a diagram showing another embodiment of the present invention. FIG. 2...Video track, 3...Overlap track, 4...Height control signal recording portion, 5...Blank portion, 9...Rotary transformer, 10...
Video head, 12... Regenerative amplifier, 1, 11...
...Magnetic tape, 14...Rotary transformer.

Claims (1)

[Claims] 1 A video head records at least a video signal and an audio signal as an FM modulated wave on a video track of a magnetic recording medium, and the video head records, for example, time-base compressed and digitized audio on a track extending from the video track. The video head is mounted on an electrostrictive element so that the height position of the video head can be controlled, and the height position of the video head is controlled to the optimum position during recording. In a magnetic recording and reproducing device that records a video signal at any position of the track with a video head, the signal for controlling the height position of the video head includes at least the video signal and an audio signal made of an FM modulated wave. A reproducing amplifier or a part thereof for recording and reproducing at a position other than the video track where it is recorded and at least amplifying the reproduced signal from the video head is built in a rotating cylinder equipped with a video head. Magnetic recording and playback device.